1. Gregor Mendel and Heredity Chapter 10.1

2. Heredity Def: passing on traits (characteristics) from parents to children

3. Gregor Mendel Austrian monk, presented work on heredity in pea plants in 1865

4. Why peas? Reproduce sexually with sex cells Could be sure of parents in a cross –Usually self-fertilize –Prevented by removing male parts, followed by manual crosses Many traits only have two forms (either/or)

5. Mendel’s Crosses Step 1 Tall (true-breeding) X Short (true breeding) –All offspring are tall

6. Step 2 Allow offspring to self-fertilize Offspring are ¾ tall, ¼ short Ratio = 3 tall : 1 short

7. Mendel repeated the experiment for 7 other traits, with the same results!Mendel repeated the experiment for 7 other traits, with the same results!

8. Mendel’s Conclusions Each organism has 2 “factors” (now “genes”) that control each of its traitsEach organism has 2 “factors” (now “genes”) that control each of its traits –different gene forms = allelesalleles When both alleles are presentWhen both alleles are present –Observed = dominant –Disappeared = recessive –Notation: alleles for same trait use same letter of alphabet, uppercase for dominant, lowercase for recessive

9. Mendel’s Conclusions Law of Segregation: every individual has two alleles of each gene. In meiosis, each gamete receives ONE of those allelesLaw of Segregation: every individual has two alleles of each gene. In meiosis, each gamete receives ONE of those alleles Law of Independent Assortment: genes for different traits are inherited independently of one anotherLaw of Independent Assortment: genes for different traits are inherited independently of one another

10. Dominant vs. Recessive NN= Black nose nn= red nose Nn=? –Black nose

11. Homozygous vs. Heterozygous If an organism’s two alleles for a trait are the same, they are homozygous for that trait. If the two alleles are different, they are heterozygous for that trait

12. NNNnnn Homozygous or heterozygous?

13. Phenotype vs. Genotype The trait that is expressed = phenotype –Hint: phenotype is physical The letter combination of alleles = genotype genotype Genotype or Phenotype? –Round –Rr –Freckled –ff

14. Both of Rudolf’s parents had black noses. –What was Rudolf’s genotype? rr –What were Rudolf’s parents’ genotypes? Rr

15. Using Punnet Squares def: a tool for predicting genetic outcomes Steps: –Write down the cross –Place each letter of the genotypes on the top and left boxes –Bring the letters down and across, pairing them in the boxes –ANSWER THE QUESTION

16. If two parents are heterozygous for eye color, what is the chance that their child will have blue eyes? Write the cross: Bb x Bb

17. If two parents are heterozygous for eye color, what is the chance that their child will have blue eyes? Write the cross: Bb x Bb

18. If two parents are heterozygous for eye color, what is the chance that their child will have blue eyes? Write the cross: Bb x Bb

19. Using Probability Remember the 2 nd law… If the genotypes of the parents are: –AaBBDd X Aabbdd What is the chance the child will be: –AABbdd?